feat(admin): add classroom edit modal

frontend/admin/admin.css

@@ -145,6 +145,74 @@ body {
     transform: scale(1.1);
 }
 
+/* Checkbox list styling */
+.checkbox-group {
+    display: flex;
+    flex-wrap: wrap;
+    gap: 12px;
+    padding: 8px 0;
+}
+
+.checkbox-item {
+    display: flex;
+    align-items: center;
+    gap: 6px;
+    font-size: 0.9rem;
+    color: var(--text-base);
+    cursor: pointer;
+}
+
+.checkbox-item input[type="checkbox"] {
+    cursor: pointer;
+    width: 16px;
+    height: 16px;
+    accent-color: var(--primary-color);
+}
+
+/* Classroom Status Badges */
+.badge-available {
+    background-color: var(--success-bg);
+    color: var(--success-color);
+}
+
+.badge-unavailable {
+    background-color: var(--error-bg);
+    color: var(--error-color);
+}
+
+.status-cell {
+    display: flex;
+    align-items: center;
+    gap: 8px;
+}
+
+.btn-icon-toggle {
+    background: var(--bg-body);
+    border: 1px solid var(--border-color);
+    color: var(--text-muted);
+    width: 28px;
+    height: 28px;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    border-radius: 6px;
+    cursor: pointer;
+    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
+    padding: 0;
+}
+
+.btn-icon-toggle:hover {
+    background: var(--card-bg);
+    border-color: var(--primary-color);
+    color: var(--primary-color);
+    transform: rotate(45deg);
+    box-shadow: 0 0 10px rgba(99, 102, 241, 0.2);
+}
+
+.btn-icon-toggle svg {
+    display: block;
+}
+
 .nav-item.active {
     background: rgba(99, 102, 241, 0.12);
     color: var(--accent-hover);
@@ -615,41 +683,60 @@ tbody tr:hover {
 }
 
 /* ===== Theme Toggle Button ===== */
-.theme-toggle {
-    width: 38px;
-    height: 38px;
-    border-radius: 50%;
-    background: var(--bg-input);
-    border: 1px solid var(--bg-card-border);
-    color: var(--text-primary);
-    cursor: pointer;
-    display: flex;
+
+/* ===== Modals ===== */
+.modal-overlay {
+    display: none;
+    position: fixed;
+    inset: 0;
+    background: rgba(0, 0, 0, 0.5);
+    z-index: 1000;
+    backdrop-filter: blur(2px);
     align-items: center;
     justify-content: center;
-    transition: background 0.3s ease, transform 0.3s ease, box-shadow 0.3s ease;
-    flex-shrink: 0;
+    padding: 1rem;
 }
 
-.theme-toggle svg {
-    width: 18px;
-    height: 18px;
-    transition: transform 0.4s ease;
+.modal-overlay.open {
+    display: flex;
+    animation: fadeIn 0.2s ease;
 }
 
-.theme-toggle:hover {
-    transform: scale(1.1);
-    box-shadow: 0 4px 16px var(--accent-glow);
+.modal-content {
+    background: var(--bg-primary);
+    border: 1px solid var(--bg-card-border);
+    border-radius: var(--radius-md);
+    padding: 2rem;
+    width: 100%;
+    max-width: 600px;
+    position: relative;
+    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.2);
 }
 
-.theme-toggle:active {
-    transform: scale(0.95);
+.modal-content h2 {
+    font-size: 1.2rem;
+    font-weight: 600;
+    margin-bottom: 0.5rem;
+    color: var(--text-primary);
+    border-bottom: 1px solid var(--bg-card-border);
+    padding-bottom: 1rem;
 }
 
-.theme-toggle--fixed {
-    position: fixed;
-    top: 1.25rem;
-    right: 1.25rem;
-    z-index: 100;
+.modal-close {
+    position: absolute;
+    top: 1.5rem;
+    right: 1.5rem;
+    background: none;
+    border: none;
+    color: var(--text-secondary);
+    font-size: 1.5rem;
+    cursor: pointer;
+    line-height: 1;
+    transition: color var(--transition);
+}
+
+.modal-close:hover {
+    color: var(--error);
 }
 
 /* ===== Responsive ===== */